Invalid URL or request options will fail silently and hang request

[Limess]

My colleague had issues where they were adding headers to a CSV file, which led to the request URL being populated as url (the string). This led to request returning an error.

Normally, this would have been handled as expected by Artillery, but in this event, request doesn't emit an error event, instead it only calls the provided callback function, see the below for a discussion on adding documentation for this:

request/request#1779

This means that either the error is completely unhandled (if maybeCallback is undefined), or caught but then ignored: https://github.com/shoreditch-ops/artillery/blob/fb681c16d7c799e1788d2eba1f84bd0f90525294/core/lib/engine_http.js#L304-L307.

The solution is to always have a callback function on this line: https://github.com/shoreditch-ops/artillery/blob/fb681c16d7c799e1788d2eba1f84bd0f90525294/core/lib/engine_http.js#L437 and to handle any errors here, rather than in the stream (or alternatively check if the callback has been called in the stream and handle errors there as well).

[hassy]

Great bug report, thanks @Limess!